A random access process needs to be initiated when a user terminal switches from an idle state to a connected state, or when the user terminal transmits uplink information in different states, such as a cell forward access state, a cell paging state or a registration zone paging state.
The user terminal transmits a preamble with an initial transmission power, particularly, the initial transmission power=a pilot transmission power−a received signal code power on a common pilot channel+an uplink interference+a constant factor of physical random access channel demodulation. Particularly, the pilot transmission power, uplink interference, and the constant factor of physical random access channel demodulation are issued by a network device through a system message, the network device may be a radio network controller (RNC) or an evolved base station (eNodeB). However the received signal code power on the common pilot channel is obtained by the user terminal by measuring the common pilot channel.
If the user terminal receives positive acknowledgment information on an acquisition indicator channel (AICH), the user terminal deems that the random access is successful and starts to transmit uplink data. If the user terminal fails to receive acknowledgment information (positive/negative) on the AICH, then the user terminal ramps up its power in a specified power step and retransmits the preamble until a maximum retransmission count is reached, or the transmission power reaches a maximum value or acknowledgment information is received on the AICH; if the power of the user terminal is ramped up to the maximum power value or number of times of retransmission reaches the maximum count or the negative acknowledgment information is received on the AICH, then a lower layer of the user terminal reports an indication to a higher layer of the user terminal, and the higher layer of the user terminal re-indicates the lower layer to initiate the random access process after waiting for a period of time, except that the preamble cycle reaches the maximum times. If the preamble cycle reaches the maximum times, but the user terminal has not yet been successfully accessed, the user terminal deems that random access is failed.
In terms of a user terminal supporting a common enhanced dedicated channel, after positive acknowledgment information is received on the AICH, further, if its own radio network temporary identity is received on an enhanced dedicated channel absolute grant channel during a collision monitoring period, the user terminal deems that a resource collision does not occur, otherwise, the collision occurs.
In the random access process, a parameter for guiding the random access is a random access parameter. The random access parameter is issued by the network device to the user terminal through the system message, and improper configuration of the random access parameter will reduce the random access success rate, increase the access delay and affect user experience. Therefore, optimizing the random access parameter is very important.
Currently, the method for optimizing the random access parameter is guiding the random access parameter optimization according to the random access report reported by the user terminal, for example, in a long term evolution (LTE) system shown in FIG. 1, the user terminal records a random access report each time when the user terminal initiates a random access process, the network device requests the user terminal to report the random access report at an appropriate moment, and the specific procedure is as follows:
S101: The user terminal records a random access report each time when the user terminal initiates a random access, where the random access parameters recorded in contents of the random access report includes number of times of preamble transmissions within each preamble cycle period and a collision indicator.
S102: The evolved base station transmits a request message to the user terminal, and requests the user terminal to report the random access report by using a random access report request indicator.
S103: The user terminal reports the random access report through a response message, after receiving the request message including the random access report request indicator.
S104: The evolved base station determines whether the random access parameter configuration is proper by counting the random access report reported by multiple user terminals and, if not proper, adjusts the random access parameter, and issues the adjusted random access parameter to the user terminal.
In the prior art, the random access parameters recorded in contents of the random access report only includes two entries of information, that is, number of times of preamble transmissions within each preamble cycle period and the collision indicator. Since the existing method for optimizing the random access parameter counts little random access information, when applied to a universal mobile telecommunication system, especially a universal mobile telecommunication (UMTS) system, it is difficult to evaluate whether the random access parameter configuration is proper with little random access information.